Modulating system



H. M. S TOL'LE R. MODULATING SYSTEM. APPLICATION FILED .DEC. 2!. 1916..

Patented Sept. 30, 1919.

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UNITED STATES PATENT OFFICE.

HUGH M. STOLLER, OF NEW YORK, Y., ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, Y., A CORPORATION OF NEW YORK.

MODULATING SYSTEM,

Specification of Letters Patent.

Patented Se t-.30, 1919.

Application filed December 21, 1916. Serial No. 138,175.-

. ing Systems, of w ich the following is a full, clear, concise, and exact description.

This invention relates to a system for modulating high frequency currents in acoordancefiwith a signal, and more particularl to modulating systems in which the radio frequency currents are obtained from a static frequency changer. A n'lodulating sys tem of this kind is shown in Figure 18 of anarLicle by Goldsmith, on Radio Frequency Che ers, appearing in Volume 3-4915 of the roceed'ings of the Institute of Radio Engineers. The frequency changer described in the article by Goldsmith comprises a magnetic structure on which are disposed low frequency and high frequency windings, and an excitation winding which keeps the magnetization of the magnetic structure near the saturation point. A modulation of the high frequency currents may be effected by varying-the excitation currents in accordance with a signal to be transmitted. This system is defective in that the varyinginduction in the magnetic strueture induces very high electromotivc forces in the excitation winding. It is a matter of considerable care and expense to provide, .for the large number of turns of the excitation winding, an insulation to withstand the high electromotive forces induced. F urthermore, the high eleetromotive forces between adjacent layers of the windings, at the hi h frequencies used, give rise to capacity e ects, and as has been recognized in connection with high frequency transformers, such capacity effects being distributed along the windin serve to short-circuit portionsof the win ing, as the high frequency power finds a path of lower impedance in such capacity than it does through the many turns of the winding. When the winding is short-circuited by the capacity effects, the efiiciency and ratio of transformation are reduced.

The present invention has forhan object I to avoid the capacity effects and 'also i thc insulation troubles. I i The invention makes use of a static frequency changer of the type disclosed and claimed in applicants co-pcnding applica tion, Serial No. 121,171, filed September 20, 19l6Frequcncy converter. An cxcitation winding is disposed on the magnetic structure in such a manner that/equal and opposing clcctromotivc forces are induced in each layer of the excitation winding. The

sum total of the electromotive forces induced capacity effects and insulation difiiculties.

are avoided.

Referring to the drawings for further details of the invention, Fig. 1 is a plan view of a magnetic modulator; Fig 2 is a cross section on line A-A, Fig. 1, looking in the direction of the arrows; Fig. 3 illustrates how the primary windings may be tapered; Figs. 4, 5 and 6 illustrate the relative geometrical relations of the different phases of; a three-phase primary winding; Figs. 7, 8 and 9 illustrate a geometrical arrangement of secondary windings for producing a three-phase secondary current having a frequency double that of the-primary currcntfFigs. 10 and 11 illustrate the prcferl'cd connection for the primary and so ondary windings respective] y; Fig. 12 illustrates a modulating system in which the modulator shown in Fig. 1 is used: Fig. 13 shows the path of the resultant of the flux where no excitation currents are used; and Fig. 14 illustrates the shift in the resultant of the flux during the flow of excitation currents.

In the particular embodiment of this invention herein illustrated, a ring shaped magnetic core 1 is provided with a plurality of projecting teeth 2 and intervening winding slots 3. Each phase of the three-phase primary windings 4-; Fraud 6 has a section on opposite halves of the core 1, the two sections being wound in opposition, as illustrated in l igs. 4, 5 and 6, respectively. Each of these primary sections may be of the tapered type, by which is meant a winding in which the number of turns per unit length of winding space-is greatest at the middle of the winding space ahd decreases in order as the end of the winding space is approached.

The reacting .electromotivc force induced by the rotating flux in theprimary windings combines with the impressed primary electromotive force to produce a resultant electromotire force that determines the prmary current. In order that there may be no distortion in the primary current the impressed and reacting clectromotiv forces should have the same wave form. A sine wave form is impressed on the primary windings and in order that a sine wave form may also be induced therein, the primary windings are tapered or distributed on core 1 as shown in Figs. l, 5 and (S.

The primaries are prete ably ring woun'd, as shown in Fig. 3, whereas a lap winding arrangement is better suited to the require ments of the secondar Figs. 7, 8 and 9 show the sect-ions of a secondary winding having twiceas many poles as the primary winding. This disposition of windings will produce a secondary frequency double the primary frequency. It will be noted that each of the secondary phase windings 7, 8 and 9 has four sections, two on each half of the core, and that adjacent sections are wound in opposite directions. It will further be noted that opposite sections are wound in the. same direction so that a diamctric field produced by the primary windings and rotating effect in the. diametrically opposed sections. it. however, the rotating licl d is shifted to one side of the diameter along the chord (,C in Fig. 7, a resultant elcctromotive force is obtaincd in the secondary winding as the two adjacent sections are wound in opposite directions and cut by lilies of flux of opposite polarity. As hereinafter explained, the

shifting of the flux is accomplished by a field circuit energized by the modulating current.

As the ratio of secondary poles to primary poles is two for each complete rotation of the field two ro ersals of current will result in each secondary phase winding, thus producing a doubling of the primary frequency;

\Vithin the core mcmberin Fig. 1 is situated the annular core member 10 which serves not only to decrease the reluctance of the path traversed by the rotating flux. but this core member also accommodates the uniformly distributed excitation winding 11 by mcans of which a modulation of the secondary current is cli'cctcd. lVhereas the rotating flux would otherwise have as a com ponent. in the direction of any diameter. a uniformly distributed unidirectional lield. the core due to its lowcr magneti reluctance may modify the flux distribiu'ion in a manner dcpcnding upon the. form and size of the core. \Vhcre the air gap is larger the field will tend to be concentrated through the core and dccrcascd through the air gap, and in effect may he considcrably constricted. \Vinding ll is disposed in the winding slot -.12 between thc teeth l3. \Vhile. the winding 11 has been shown as having within the core 1 will produce no only two layers, as a matter of fact this winding would consist of probably one hundred or more layers. The excitation winding 11 is of the ring type and is Wound throughout its length in the same direction, and the terminals 32, 33 (Fig. 12) of this winding should be brought out at the same points on the circumference of the winding so that each layer of the' winding may be circumfcrentially complete. The band of rotating flux which cuts the winding 11 will induce in each half of every layer of this winding an clectromotive force substantially equal. to and opposing, the electromotive force induced in the other half ofcach layer of this winding. tire forces in each layer of the winding ll combine to produce a zero potential, and insulation diffieultics and undesirable capacity et'fects are thereby avoided.

Fig. 12 show a molulating system in which the modulator shown in Fig. 1 may be used. In Fig. 12 the primary winding l. 3, (i is connected to a suitable source 42 of three-phasecurrent. Two of the terminals of the secondary winding 7, S, Q are connected in the antenna system 43, ll, 15. In circuit with the excitation winding 11 is the battery 10 and a step-up transformer 17 of suitable voltage. ratio. which serves to couple the circuit including the winding 11 and battery 16 to a signal circuit 18. In the circuit 18 are provided a suitable source of current ll) and a signal device 20., which may be a microphone transmitter.

The thrcc-pha e current of a given frequcncy vsupplied by source 42 to the primary winding -l-. 0, prmluccs a double frequency in the antenna line 43, ll, 7, S, 15. The variations in current produced in circuit 18 by the signaling device 20 are impressed by means of transformer 17 on the excitation winding 11. The conscqucnt variation in the current in the excitation winding produccs a variable field which proportionally shifts the rotating field to a chordal position such as represented by line CC, Fig. 7, for the following rcasons: If there is-no current in the excitation winding, the distribution of the flux in the core members 1 and 10 may be considered as a constricted field along any diameter IL-B as shown in Fig. $3. The flux crosses the air-gap at diametrically opposite points. for instance, on the diamctcr B B. which may be considered as rotating in the plane of the paper about the ccntcr 30. The winding 11 when energixcd produces in the. core member 10 a flux which takes the circular path 31. as shown in Fig. 14. The flux in the. path 31 aids the main tiux at one sidc of thc core'1() thereby imrcasingthc saturation and the reluctance. and. at the other side of core 10 the two fluxes oppose. minimizing thc saturation and the reluctance. The main flux now crosses The opposing electromo-- the air-gap at pointsnearer the unsaturated portion of the core 10, these points being,

for instance on the chord CC which rotates about the center 30. The electromotive force induced in the secondary windings depends upon the distance of the chord C-C from the center 30 as explained above, The bat tery 16 gives to the rotating field a constant shift which is increased or decreased in ac-,

' windings by the rotating magnetic field because of the shift of this field produced by the magnetizing current from source 16, the primary and secondary windings are considered as inductivelyrelated, while the excitation winding 11 which has balanced electromotive forces, substantially neutralizing each other, induced by the rotating field, whether in its diametral or shifted position, is considered as non-inductively related to the other two windings.

What is claimed is:

1. in a modulating system, the combination of magnetic means, primary and secondary windings inductively related to said magnetic means, means for supplying oscil lations of a given frequency to said primary windings, and an excitation winding com prising means so disposed with relation to said magnetic means that the flux in the latter induces substantially equal and opposing electromotive forces in said excitation wind ing, said secondary windings comprising means for supplying modulated waves having a frequency higher than that of the 0s cillations supplied to said primary windings.

2. Ina modulating system, the combination of magnetic means, primary and secondary windings inductively related to said magnetic means, the number of poles of said secondary windin, being a multiple of the primary poles, an an excitation winding so disposed with relation to said magnetic means that the flux therein induces substan tially equal and opposing electromotive forces in said excitation windin 3. In a modulating system, tie combination of two concentric core members separated by an air-gap, polyphase prn naryi:

windings on one of said members for producing a rotating magnetic field across said gap, a secondary winding in the path of said rotating field, an excitation winding on one of said members and means for supplying current varying in accordance with signals to said excitation winding.

4. In a modulating system, the combination of magnetic means, tapered polyphase primary windings and multi-section seconding in the path of sai ary windings inductively related to said magnetic means, the adjacent sections of said secondary winding being wound in opposite directions, and a circumferentially complete excitation winding inductively related to said magnetic means.

5. In a modulating system, the combination of two concentric core members separated by an air-gap, polyphase primary windings on one of said members for producing a rotating magnetic field across said gap,- a secondary winding in the path of said rotating field, and a UHIfOIIIIlY distributed excitation winding of the ring type wound in the same direction throughout its length on one of said members,

6; A modulating system comprising means for producing a rotating flux, a winding in the path of said fiuxfmeans for causing said flux to rotate unsymmetrically with respect to said winding, and means for varying the position of said flux with respect to said winding in accordance with a signal to be,

transmitted whereby the current in said winding is modulated in accordance with said signal. I V

7. In a signaling system, the combination of means for producing a rotating flux, a winding in the path of said flux, said winding having a plurality of sections and adjacent sections being wound in opposite directions, and means for varying the relative position of said flux and said windin in accordance with a signal to be transmitted whereby a modulation of the lower delivered by said winding is effected 8. A modulating system comprising ma netic means, primary and secondary windings inductivel related to saidv magnetic means, means tor supplying oscillations of a given frequency to said primary winding, an excitation winding comprisin means so disposed with relation to sai magnetic means that the flux in the latter induces in said excitation winding a plurality of electromotive forces the resultant of which is zero, a source of power for said primary winding, means for transmitting from said secondary winding modulated waves having a a frequency higher than that of the oscillanetic field across said ga a secondary 'win rotating field, the number of poles in said secondary winding being a multiple of the primary poles, an excitation winding of the ring type on one of said members, a source of power forsaid primary-windings, means for transmitting power from said secondary winding, means for supplying a constant current to said eX- citation winding, and a signaling device as sociated with said excitation winding.

10. A magnetizable member, three Windings associated therewith, two of said Windings being inductively related and the third winding being noninductively related to the other two and means for supplying oscillations of a given frequency to one of said two inductively related windings, the other of said windings serving as means for supplying waves of a frequency different from that of said oscillations.

11. A inagnetizable member, primary, secondary and excitation windings associated therewith, said primary and secondary windings being inductively related and said excitation winding being noninductively related to said other windings, a source of oscillations in circuit with said primary Wind ing, said secondary winding comprising means for supplying modulated waves of frequency different from that of said osc'il lations, and a modulating device associated with said excitation winding.

12. In combination, means for producing a rotating magnetic field, a winding'so re lated to said means that'the electromotive forces induced therein by said field substantially neutralize each other, and means for shifting said field to produce a resultant electromotive force in said winding.

13. In a signaling system, means for roducing a rotating magnetic field, a winc ing so related to said means that the electroinotive forces induced therein by said field substantially neutralize each other, and means controlled by signals for shifting said field so as to cause a resultant electromotive force to be set up in said winding.

1-1. A primary winding having portions wound in different directions to produce poles, means for supplying alternating current to the primary winding to produce a rotating magnetic field, a secondary winding associated therewith and wound so as to produce a number. of poles which is an even multiple of the number of poles produced by the primary winding, whereby no resultant electromotive force is produced in the secondary winding, and means for shifting said rotating magnetic field to cause an electromotive force to be set up in the secondary winding. y

In witness whereof, I hereunto subscribe my name this th day of December A. D.

HUGH M. STOLLER. 

